Kevin Pietersen must put down in writing a pledge to make himself available for the next two Ashes series, according to former England captain Michael Vaughan.

Pietersen retired from all forms of international limited-overs cricket on Thursday, citing the "intensity of the international schedule", but said he still wanted to play in Tests for Andy Flower's side.

ECB managing director Hugh Morris expressed frustration at the timing of the announcement, and Vaughan feels Pietersen should mend some bridges by firming up his desire to compete in the five-day format.

"If I was a member of the England management I would want a written promise from Kevin Pietersen that he is committed to playing in the next two Ashes series," Vaughan said in the Telegraph.

"I would want to know that he is not going to suddenly have another great IPL season, make a load more money and then pull the plug on his Test career in the lead-up to next summer's Ashes.

"If he has got any thoughts of quitting Tests in the next 12 months he has to be honest and tell Andrew Strauss and Andy Flower now, so they have time to bed in someone else. Personally, I think he is committed to Test cricket and the Ashes. He loves Test cricket. It gives him a buzz."